# AliasBasedKeyManager.java

    /*
     * Copyright (c) 2025, WSO2 LLC. (http://www.wso2.com).
     *
     * WSO2 LLC. licenses this file to you under the Apache License,
     * Version 2.0 (the "License"); you may not use this file except
     * in compliance with the License.
     * You may obtain a copy of the License at
     *
     * http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing,
     * software distributed under the License is distributed on an
     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     * KIND, either express or implied.  See the License for the
     * specific language governing permissions and limitations
     * under the License.
     */

    package org.apache.synapse.transport.nhttp.config;

    import javax.net.ssl.SSLEngine;
    import javax.net.ssl.X509ExtendedKeyManager;
    import javax.net.ssl.X509KeyManager;
    import java.net.Socket;
    import java.security.Principal;
    import java.security.PrivateKey;
    import java.security.cert.X509Certificate;
    import java.util.Arrays;

    /**
     * Custom X509KeyManager that selects a specific alias for client and server certificates
     */
    public class AliasBasedKeyManager extends X509ExtendedKeyManager {
        private final X509KeyManager keyManager;
        private final String preferredKeyAlias;

        public AliasBasedKeyManager(X509KeyManager keyManager, String preferredKeyAlias) {
            this.keyManager = keyManager;
            this.preferredKeyAlias = preferredKeyAlias;
        }

        @Override
        public String[] getClientAliases(String keyType, Principal[] issuers) {
            return keyManager.getClientAliases(keyType, issuers);
        }

        @Override
        public String chooseClientAlias(String[] keyType, Principal[] issuers, Socket socket) {
            return keyManager.chooseClientAlias(keyType, issuers, socket);
        }

        @Override
        public String[] getServerAliases(String keyType, Principal[] issuers) {
            return keyManager.getServerAliases(keyType, issuers);
        }

        @Override
        public String chooseServerAlias(String keyType, Principal[] issuers, Socket socket) {
            String[] aliases = keyManager.getServerAliases(keyType, issuers);
            if (aliases != null && Arrays.asList(aliases).contains(preferredKeyAlias)) {
                return preferredKeyAlias;
            }
            return keyManager.chooseServerAlias(keyType, issuers, socket);
        }

        @Override
        public String chooseEngineServerAlias(String keyType, Principal[] issuers, SSLEngine engine) {
            return chooseServerAlias(keyType, issuers, (Socket) null);
        }

        @Override
        public X509Certificate[] getCertificateChain(String alias) {
            return keyManager.getCertificateChain(alias);
        }

        @Override
        public PrivateKey getPrivateKey(String alias) {
            return keyManager.getPrivateKey(alias);
        }
    }